The formal complaint states, "At the time of the experiment, Facebook did not state in the Data Use Policy that user data would be used for research purposes. Facebook also failed to inform users that their personal information would be shared with researchers."

While Facebook has not issued an apology for the experiment itself, they were quick to reply to EPIC's formal complaint. "When someone signs up for Facebook, we've always asked permission to use their information to provide and enhance the services we offer. To suggest we conducted any corporate research without permission is complete fiction," Facebook said in a statement."Companies that want to improve their services use the information their customers provide, whether their privacy policy uses the word 'research' or not."

News reports are focusing on the Germanwings pilot's possible depression, following a familiar script in the wake of mass killings. But the evidence shows violence is extremely rare among the mentally ill.